To employ therapeutically the drugs described in this work is not to experiment "in anima vilis," as some would have us believe. To experiment is to employ unknown remedies of unknown virtues and properties. In this treatise I am not attempting to fix the indications for this or that product, but simply make known the diseases in which the Filipinos and the natives of other countries employ the products. Any physician has a perfect right to prescribe these drugs, as have also the "curanderos" and even the laity, with this difference, however, that the physician is capable of observing results and guiding himself by the physiologic action of the drugs. His knowledge of the physiologic and anatomo-pathologic problems of the human body, will enable the physician to make scientific inferences that would be hidden from the common "curandero." As neither the Manila nor the provincial physicians keep these medicinal plants in stock, with the exception of those that are official in the European and American pharmacopoeias, it will be necessary for the physician who wishes to use them, to busy himself with seeking them and laying in a sufficient stock to serve him when the opportunity presents itself. It is necessary to preserve them by drying and this is best done by exposing them several days to the fresh air in a dry place--for example, the corridors of the house--being careful not to expose them to the rays of the sun, in which latter event the fleshy and juicy plants which do not desiccate rapidly, putrefy or ferment. A convenient way to get them is to visit the Binondo Square where there has been market for native drugs from time immemorial. The gardeners from the neighboring towns, especially those from Pasay and Singalon, regularly offer the plants for sale and will undertake to supply you with any that may not be on hand. Inasmuch as the common names of the plants lead to many mistakes and much confusion, it is indispensable to acquaint one's self with the description of the plant and be sure that the actual product conforms in all respects to the description. For this purpose it is well to obtain flowering specimens, and bearing this fact in mind I have been careful to indicate the flowering season of each plant. By making excursions to the towns of San Mateo and Angono I have obtained an abundance of whatever I sought and at the same time have learned by talking with the mountaineers and "curanderos," what uses they make of their plants. The "curanderos" know a great deal concerning these uses, but become very reticent as soon as they are questioned about them. Whether it is dread of ridicule or selfishness or fear that silences them, the fact remains that it is no easy matter to glean any useful facts from them. And yet by tact and friendliness one may elicit much more information from them than first impressions would lead one to hope. Leaves should be gathered when fully developed, rejecting the old, dried and worm-eaten ones.